diff --git a/YASI_12/ds.LinearProbingHashTable.h b/YASI_12/ds.LinearProbingHashTable.h
index a4ed956..aac6a75 100644
--- a/YASI_12/ds.LinearProbingHashTable.h
+++ b/YASI_12/ds.LinearProbingHashTable.h
@@ -213,7 +213,7 @@ namespace ds{
 		}
 
 		virtual void put(const Key& key, const Value& value) override { return insert(key, value); }
-		virtual bool contains(const Key& key) const override { return lookupKey(key) == NULL; }
+		virtual bool contains(const Key& key) const override { return lookupKey(key) != NULL; }
 		virtual void remove(const Key& k) override {
 			// zero key
 			if (k == 0){